The crosslinking of polymers by various methods to achieve certain improved physical properties is well known in the art. The particular method of modifying polymers by azidosilanes and further crosslinking is known as for example in U.S. Pat. No. 3,697,551 to Thomson. Furthermore, the crosslinking of particular polymers such as polyethylene and polyethylenebutene copolymers after exposure to sulfonylazides and, subsequently, moisture is known as for example in U.S. Pat. No. 4,551,504 to Barnabeo. In addition, the subsequent moisture crosslinking of polymers previously exposed to a monovalently olefinically unsaturated silane and a peroxide have been disclosed as, for example, in U.S. Pat. No. 3,646,155 and U.S. Pat. No. 4,247,667.
Also, a method which describes polymers which have been modified with .gamma.-methacryloxypropyltrimethoxysilane in the presence of peroxides has been disclosed in U.S. Pat. No. 4,032,592. And polyolefin blends which contain a polyolefin which has been modified with an olefinically unsaturated silane and a peroxide have been disclosed in U.S. Pat. No. 4,533,602.
Furthermore, polyethylenes which have been grafted with trimethoxyvinylsilane and a peroxide to give gel contents of about 23% to 78% and which are used to produce foams in the presence of 0.2 to 30 percent of a foaming agent such as azidocarbonamide based materials have been disclosed in U.S. Pat. No. 4,413,066. And polyolefin resins which are modified by trimethylvinylsilane with peroxide and are foamed by, and reacted with, water are disclosed in U.S. Pat. No. 4,591,606.
Also, polyolefin precoat compositions containing azidosilane crosslinking compounds have been described in U.S. Pat. No. 4,552,794.